Special Coatings for Artificial Turf

ABSTRACT

An artificial turf surface comprised of natural looking fibrous materials is coated with special heat reflecting materials that do not alter the appearance of the fibers, but reflect unwanted heat. Both turf blades and beads can be coated. A process and method is also described in which artificial turf can be cleaned and coated in the field after installation and specially coated, flexible mini beads can be added as filler.

This application is related to, and claims priority from, U.S. Provisional Patent Application No. 61/507,711 filed Jul. 14, 2011. Application 61/507,711 is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention pertains generally to artificial turfs and in particular to artificial turf coatings.

2. Description of the Prior Art

Artificial turfs or synthetic turfs are known typically as grass-like, man-made surfaces manufactured from synthetic materials. This turf can be used in homes, commercial and industrial properties, and resorts and also used in recreational areas and common areas for multiunit dwellings and also arenas for sports that were originally played on natural grass. The use of artificial turf is expanding rapidly. The first artificial turfs developed and installed were far harder than grass. Their use was limited due to a bad reputation, appearance, and claims that the hard surface caused injuries to participants in sports activities.

New artificial playing surfaces using sand and/or rubber infill have more recently been developed. These artificial grass surfaces are often virtually indistinguishable from grass when viewed from any distance, and are generally regarded as being about as safe to play on as a typical grass surface.

Many sports clubs have decided to install synthetic turf surfaces due to their lower maintenance costs and improved play in colder conditions. However, it is the warmer conditions that are causing most concern for players.

Most common types of artificial turf uses polyethylene “grass” 2 to 8 centimeters long, which is lubricated and tufted into a woven backing fabric the rear of which is coated with a polyurethane or latex backing medium to lock the tufts in to place. This mat of turf can be filled to the client's specification with sand and rubber granules which keeps the fibers upright and provides the right level of shock absorbency. The majority of the turf manufacturers approved by various sports associations use this technology. In some applications of the turf, it is also interspersed with short, curly, spring-like fibers that keep the blades upright. Sometimes a rubber layer can also be added.

Although artificial turfs are mostly applied in sporting venues, the term “artificial turf” encompasses any applications or modifications that lead to synthetic grass, i.e. grass that is made of a synthetic material (usually a polymer such as polyethylene or polypropylene). Such applications also include but are not limited to landscape applications and to green roofs on buildings.

The components used for artificial turf surfaces include—as mentioned above—fibers, filaments and tapes, and if applicable infill materials.

While already having advantages over natural grass surfaces in cold areas or in the wintertime, the overall comfort of artificial turfs in hotter climates or seasons is still a problem.

U.S. Pat. No. 3,740,303 discloses an artificial playing surface that comprise a pile fabric with pile fibers having pigments and materials to stabilize against UV light. These stabilizers usually are sterically hindered amines that catch the radicals generated by the energy of the UV light.

US 2004/0214000 is directed to aggregate turf filler for use with the turf of athletic fields and landscape area, which comprise crushed silica sand particles. Such fillers may be colored to enhance the appearance of the surface.

U.S. Pat. No. 5,958,527 discloses a synthetic grass turf with a unique multiple course resilient particulate infill. The infill consists of brightly colored sand and may serve the purpose to reduce the heat retention of the infill.

US 2003/0056432 discloses a synthetic grass surface with widely spaced rows of ribbons projecting from a flexible backing sheet which grass surface comprises thermal regulation means attached to the backing sheet in the spaces.

DESCRIPTION OF THE FIGURES

Attention is now directed to several drawings that illustrate features of the present invention:

FIG. 1A shows a cross-section of an embodiment of the present invention.

FIG. 1B shows an expanded view of a ribbon turf blade.

FIG. 1C shows mini-beads as a filler at the base of the turf blade.

Several illustrations and drawings have been presented to aid in understanding the present invention. The scope of the present invention is not limited to what is shown in the figures.

DESCRIPTION OF THE INVENTION

The present invention relates to an artificial turf that offers comfort and safety both under hot and cold conditions, and which can easily and reliably be added during the manufacturing process or any time thereafter. There is a standard manufacturing process known to someone skilled in this area that involves attaching the blades to the backing material. The coating process that we will describe can take place either before or after the blades are attached to the backing material. Of course, once installed in the field the coating process must take place with blades already attached to the backing material. After the backing material and ribbons are combined to make the turf that is the finished product ready to be shipped to customers, the customer then has the option of ordering the turf with or without the IR reflective coating. The coating can also be added “in the field” with a roller or spray coating process.

FIG. 1A shows an example of an artificial turf according to the present invention. A foundation layer 1 is covered with a backing material layer 2. Ribbons 3 of polymer form turf blades with infill material 5 between them. Each turf blade 3 of the present invention is typically coated with an IR-reflective coating 4 to reduce solar absorption and heating. FIG. 1B shows a detail of a turf blade. The IR coating 4 can be in the form of small particles or powder held in a binder 6. Alternatively it can be a continuous coating.

This objective is achieved by an artificial turf coating that includes mixed metal oxides that are IR reflective materials, wherein the surface of the blades of the artificial turf is coated by methods, including a spraying process, an immersion process and a roller coating process. Mixtures of metal oxides can be created in order to reflect IR radiation. The coating reflect(s) IR light thus keeping the surface cooler than non-coated turf. The preferred coating is a roller process because this allows for various types of binders to be used to bind the IR reflective pigments to the surface of the turf blades. The preferred pigments are comprised of mixed metal oxides. The preferred coating for the artificial turf blades is a green colored pigment from Shepherd Color's Artic line of IR reflective pigments.

In contrast to the prior art, the present invention restricts the presence of the additives and pigments to be incorporated into a coating to a preferred location at the surface of the fibrous material. The present invention also contemplates adding pre-coated, IR reflective mini-beads as a filler that will migrate to the base of the blades and reflect unwanted IR radiation that penetrates the upper levels of the blades. The IR reflective coating leaves the other properties of the fibrous material substantially unchanged, which is important for the suitability of the artificial turf for such uses as ball rolling and running and the like. The goal of the coating process is to have the IR reflecting material adhere to the surface of the blades, while at the same time maintaining the same feel and characteristics of real, natural blades of grass in natural turf, especially as the surface might effect the true roll of a golf or soccer ball.

Typically, an artificial turf assembly includes a pile fabric with a flexible sheet backing and rows of upstanding synthetic ribbons tufted through the flexible backing representing grass blades extending upwardly from an upper surface of the backing. Synthetic ribbons are preferred as a way of making artificial grass blades as well as the preferred surface for applying additives and IR reflective pigments.

Measurable IR light and heat reflectance can be achieved by the addition of the reflective additives and pigments to the surface of the ribbons. As mentioned, heat reflectance can also be achieved by applying IR reflective coated rubber mini-beads as a filler. Flexible beads approximately 6 mm in diameter can be added to artificial turf in order to cushion the impact of a player's shoe or foot on the surface. These same beads can be coated with IR reflective material which reflect the IR radiation that penetrates through the blades, or reflects off of the blades in a downward fashion so as to heat the area at the base of the blades with unwanted IR radiation. The flexible mini beads can be pre-coated in a manufacturing process in which they are immersed or sprayed or rollered with the IR reflective material. The coated beads are then dried so that they do not stick to each other and will roll easily and freely on the surface of the turf allowing natural effects of gravity and normal usage to allow them to migrate towards the base of the blades where they will sit atop the backing material to which the blades are attached. This is shown in FIG. 1C where the coated beads 7 can be seen gathered at the base of the blades 3. Artificial turf surfaces without these additives and pigments are much hotter to the touch during the hot summer months than those with such additives. The preferred additives are mixed metal oxides pigments to be added to the binder that will adhere to the surface of the mini beads. Different ratios and different colors of pigments can be used on the mini-beads.

While the preferred additives are as described above, additives and pigments can be any IR reflective materials that do not appreciably alter the visual appearance of the turf. Any such additive or IR reflective material is within the scope of the present invention.

As discussed, the term IR means infra-red and is used to mean a range of wavelengths of the total solar reflectance which is in the infra-red range, typically longer than 700 nm in wavelength. Reflectance of IR light prevents the turf from heating in sunlight. The higher the solar reflectance, the cooler the object will be. Preferably, reflectance is appreciable in the wavelength range of light from approximately 700 nm to approximately 1 um or longer.

Particularly preferred is the reflectance of the heat radiation in the infrared spectrum since IR makes up over 50% of the solar spectrum, and is thus a significant portion of the sun's heat energy. For this reason additives and pigments with an increased reflectance in the so-called near infrared (NIR) range, i.e., in the wavelength range from about 700 nm to about 1 micron or longer. The light reflectance should be at least as high as that of a natural grass turf surface. It is preferred for it to be 10% or even 20% higher than that of a natural grass turf surface.

The preferred additives or pigments have the property to reflect heat generated by sunlight and other light or heat sources in at least the same order of magnitude as the chlorophyll in natural turf does. Prior art pigments currently in use in artificial turf generally have a higher IR absorption than chlorophyll.

Preferably, the additive(s) or pigment(s) are coated over the fibrous material or ribbons using a spray, or a roller coating process. It is also within the scope of the present invention to use an immersion or dipping process. Each method requires a special vehicle or binder designed to bind to the blade material. The mixed metal oxide pigments are inert and are compatible with various binders, including aqueous, polyester, acrylics and fluoropolymers.

Another aspect of the invention is to use a UV curing vehicle to bind the pigments to the surface of the artificial turf blades. Both the pigments themselves and the turf blades are designed to be UV damage and fade resistant. The coated surface containing the pigments will reject the IR part of the spectrum; however, the binder will absorb the UV part of the spectrum and help to cross link the UV curing vehicle to the blade's surface. This will be especially suitable if spray coating or roller coating an outdoor surface during a sunny day when the solar radiation will act to bind the IR reflective pigments in the UV activated binder to the blade's surface. In an indoor setting, or if treating an outdoor field at night, standard UV lights with wavelengths from approximately 300 nm to 400 nm will be adequate to trigger the curing process of the binder material containing the pigments to the surface of the blades.

Several binder solutions are available for this application. An important function of the coating process is choosing the binder that will carry the pigments in the proper load ratio and at the same time adhere to both the pigments and the polyethylene blades upon drying. There are various families of binders used in this process, most in the acrylate family. Also of interest as mentioned above, are the binders that cure using UV radiation for cross-linking. UV curing binders are well understood by a person skilled in the art.

Another potential binder is based on Silicon chemistry. It also contains cross-linking agents, which are used in many applications requiring improved adhesion and also water-resistance. This chemistry provides high adhesion to glass and some plastic surfaces.

Use of cross-linking agents in coatings is common and can be used to adhere to various plastics, including polyethylene. Although typically they are used at levels of about 1%, they can have a major effect on adhesion and product stability in the field, but undesirable side effects can occur, including increased viscosity, discoloration, and odor. Care must be taken to avoid these effects.

Another potential additive to a binder is toluene. Toluene is a common solvent, able to dissolve paints, paint thinners, silicone sealants, rubber, inks and adhesives. It can also be used to bind IR reflective pigments to a polyethylene surface. It is currently used as the active ingredient in a spray paint that binds colored pigments to plastic surfaces. Toluene does this by partially dissolving and fusing to the plastic surfaces.

Thermoplastic solution resin blends are also a good carrier and binder for the inorganic heat-reflective pigments. The preferred binder product contains a blend of vinyl and acrylic resins, a blend of solvents, one or more heat-reflective pigments, and performance additives.

In the preferred thermoplastic coating, the binder film is formed by evaporation of the solvents rather than by cross-linking reactions. Since no cross linking occurs, the resin monomers and co-monomers must be chosen for film forming performance, as well as for other characteristics that are desirable in the applied coating. Thermoplastic acrylic and vinyl coatings show minimal yellowing or cloudiness after drying, have excellent outdoor durability, and have excellent adhesion to polyethylene. Thermoplastic resin coatings also show outstanding adhesion to natural and synthetic rubber materials, such as mini beads and natural fiber materials that may appear in the aggregate synthetic turf.

Long-chain, high molecular weight polymers show the best durability, but may also have high viscosities that prevent spray application of the coating; therefore, the preferred method for applications is roller coating or immersion coating if done in the manufacturing facility and roller coating if done later after being installed in the field. A suitable solvent blend can address the requirements of low viscosity, speed of evaporation after application, good adhesion to polyethylene, and low toxicity. UV-absorbing additives can be added to increase the outdoor durability of the coating.

Coating, rolling and immersion processes are preferable to extruding the pigments in the fibers and blades. The process of the present invention guarantees that the pigments are only found at the surface of the blade where the optimum amount of IR light can be reflected and rejected.

There are two ways to achieve IR reflectance and a natural looking color for the turf. One way is to apply a clear coating of IR reflective pigments that do not effect the underlying color of the turf blades. The second, preferred method is to match the underlying color of the turf. The Shepherd Color Company has developed a family of highly efficient IR reflective pigments that can achieve a color quality that highly resembles the underlying “natural” green color of the turf blades. These pigments include mixed metal oxides that are also called complex inorganic colored pigments.

Any pigment that is capable of reflecting infra red light can be used as an additive as long as it can be added to a binding solution. It is preferred to apply as additives those pigments that are selected from a group containing metal oxides, mixed metal oxides, cobalt compounds and chromium compounds such as titanium dioxide, aluminum, and chromium oxide pigments. These pigments are stable in full sunlight and will last many years.

Further additives and pigments of the class of metal-oxide titanates based on antimony, chromium, tin and cobalt can be used. These pigments are all non toxic and have both FDA and EEC purity approvals in the quantities used.

After artificial turf has been in service, generally there can be an after-market cleaning and possibly re-coating process. For this process, a novel method can be used to both coat the blades and also add flexible beads to the artificial turf according to the present invention. This method involves using a device that can be added to the front and rear of a motive device such as a tractor. The front of the tractor can be devoted to vacuuming dirt, debris and unwanted metallic pieces, such as tacks or nails from the surface. Optionally there can be a powerful magnet in series to attract metal to the surface to either stick to the magnet or to be sucked up into the vacuum. This process also pulls the blades up vertical so that they are more easily reached in the next step which is wet cleaning. In this step, a cleaning detergent solution is brushed into the surface of the turf. The detergent can be washed away with water or other solution and another vacuum process can be initiated. A drying process can then be begun as the tractor moves slowly over the surface. Again the blades are pulled vertical. The IR reflective pigments mixed into the binder solution can then be sprayed or rolled or brushed onto the surface of the turf. The final step, if requested by the customer, can be the addition of IR coated, flexible mini beads into the turf as a filler.

Artificial turf blades having their surfaces coated according to the present invention exhibit a considerably reduced surface temperature.

The present invention is especially advantageous for sport fields and landscape applications to increase the player's and user's comfort and safety. Another important aspect of this invention is energy savings in applications where artificial turf is used as an insulation material to prevent heat build up on any surface.

Several descriptions and illustrations have been presented to aid in understanding the present invention. One with skill in the art will understand that numerous changes and variations can be made without departing from the spirit of the invention. Each of these changes and variations is within the scope of the present invention. 

We claim:
 1. A method for keeping artificial turf having a plurality of turf blades cool in sunlight comprising: coating each turf blade with and IR reflective coating, said IR reflective coating containing metal oxides to form coated turf blades; coating a plurality of beads with said IR reflective coating to produce coated beads; drying the coated beads after said coating step; adding a layer of said coated beads at the base of the coated turf blades.
 2. The method of claim 1 wherein said metal oxides include at least one of titanium dioxide, aluminum oxide or chromium oxide.
 3. The method of claim 1 wherein light reflectance of said coated beads and coated turf blades is at least 10% higher than natural turf.
 4. The method of claim 1 wherein said beads are approximately 6 mm in diameter.
 5. The method of claim 1 wherein said turf blades are coated by immersing, spraying or rollering.
 6. The method of claim 1 wherein said beads are coated by immersing, spraying or rollering.
 7. The method of claim 1 wherein said metal oxides are contained in a binder chosen from the group consisting of aqueous binders, polyester binders, acrylic binders and fluoropolymer binders.
 8. The method of claim 2 wherein light reflectance of said coated beads and coated turf blades is at least 10% higher than natural turf.
 9. The method of claim 8 wherein said beads are approximately 6 mm in diameter.
 10. The method of claim 9 wherein said turf blades are coated by immersing, spraying or rollering.
 11. The method of claim 10 wherein said metal oxides are contained in a binder chosen from the group consisting of aqueous binders, polyester binders, acrylic binders and fluoropolymer binders.
 12. The method of claim 11 wherein said binder is UV cured.
 13. The method of claim 7 wherein said binder is UV cured.
 14. A method for producing an artificial turf comprising: rollering an IR reflective coating onto a plurality of turf blades attached to a base; spraying said IR reflective coating onto a plurality of approximately 6 mm beads; drying said beads; placing a layer of said beads on said base around said turf blades.
 15. The method of claim 14 wherein said IR reflective coating contains metal oxides.
 16. The method of claim 15 wherein said metal oxides include at least one of titanium dioxide, aluminum oxide or chromium oxide.
 17. The method of claim 14 wherein said metal oxides are contained in a binder chosen from the group consisting of aqueous binders, polyester binders, acrylic binders and fluoropolymer binders.
 18. An artificial turf comprising: a turf backing including: a plurality of turf blades roller coated with an IR reflective coating attached to said backing; a layer of beads coated with said IR reflective coating in proximity to said turf backing; wherein, said IR reflective coating contains a metal oxides in a binder.
 19. The artificial turf of claim 18 wherein said metal oxides include at least one of titanium dioxide, aluminum oxide or chromium oxide.
 20. The artificial turf of claim 18 wherein said binder is chosen from the group consisting of aqueous binders, polyester binders, acrylic binders and fluoropolymer binders. 